Purified polypeptides having IL-13 receptor activity

ABSTRACT

This invention relates to a purified polypeptide comprising an amino acid sequence chosen from the sequence SEQ ID NO:4 or biologically active amino acid sequences derived from SEQ ID NO:4.

The present invention relates to purified polypeptides having a receptoractivity specific for interleukin-13 (IL-13), to their biologicallyactive fragments and to the corresponding nucleic acid sequences and totheir applications.

IL-13 is a recently identified (1, 2) cytokine of 112 amino acidssecreted by the activated T lymphocytes, the B lymphocytes and themastocytes after activation.

By virtue of its numerous biological properties shared with IL-4, IL-13has been described as an IL-4-like cytokine. Its activities are indeedsimilar to those of IL-4 on the B cells (3-5), the monocytes (6-10) andother non-haematopoietic cells (11-12). On the other hand, contrary toIL-4, it would not exert a specific effect on resting or activated Tcells (13).

Various biological activities of IL-13 on the monocytes/macrophages, theB lymphocytes and certain haematopoietic precursors have been describedin detail by A. J. Minty, as well as in review articles on IL-13 (seefor example 14). Several data indicate, in addition, that this cytokinehas a pleiotropic effect on other cell types. These non-haematopoieticcells which are directly affected by IL-13 are endothelial andmicroglial cells, keratinocytes and kidney and colon carcinomas.

The anti-inflammatory and immunoregulatory activities of IL-13 may beuseful, for example, in the treatment of autoimmune, tumour and viralpathologies.

An exploitation of these biological properties at the clinical levelrequires, however, a perfect knowledge of the signals and mechanisms viawhich these effects are exerted, so as to be able to control andmodulate them in the relevant pathologies.

One of the stages in the analysis of the signal transmitted by abiological molecule within a cell consists in identifying its membranereceptor. The research studies carried out to this end on the IL-13receptor have shown that IL-13 and IL-4 had a common receptor, or at thevery least some of the components of a common receptor complex, as wellas common signal transduction elements (15-18). This receptor is presentat the surface of various cell types, in a variable number according tothe cell type considered. The comparative distribution of the IL-13 andIL-4 receptors has been indicated by A. J. Minty (14).

Kondo et al. (19) have described the structure of a receptor having ahigh affinity for IL-4. This receptor is a dimer, formed by theassociation of a glycoprotein of 140 kDa (IL-4R) and of the γ chain ofthe IL-2 receptor (γc). IL-4 can bind to the glycoprotein subunit of 140kDa (IL-4R or gp 140) with a high affinity (Kd between 50 and 100 pM)(15). However, this affinity is increased by a factor of 2 to 3 when theγc chain is associated with gp 140. This association is, in addition,necessary for the transmission of certain signals mediated by IL-4 (19,20).

Cross-competition experiments for binding either of IL-13 or of IL-4have demonstrated that IL-4 can normally prevent the binding of IL-13,whereas IL-13 can generally only partially prevent the binding of IL4 toits receptor (17, 21) and does not attach to any of the two subunits ofthe IL-4 receptor or to the complex formed by their association. On thebasis of these observations, the authors of the present invention haveassumed that the receptor specific for IL-13 consisted of the receptorcomplex IL-4 associated with another IL-13 binding component (IL-13Rβ).

Research studies carried out on an erythroleukemic cell line capable ofproliferating in response to IL-13 and IL-4 (TF-1 line) allowed them toshow that these two cytokines produced similar intracellular eventsafter attachment to their receptor (18). In parallel, cross-linkingexperiments allowed them to show that gp 140 could form heterodimerseither with the γ chain, or with a new subunit, of a molecular weight of55 to 70 kDa (17, 21).

Moreover, research studies recently carried out on a mouse embryonicstem cell line have made it possible to isolate the genomic DNA and thecDNA encoding a polypeptide of 424 amino acid residues (IL-13Rα),suggesting that the IL-13 receptor shared with the IL-4 receptor acommon chain so as to constitute a high-affinity receptor (22, 23), thatis to say has an affinity whose constant Kd is situated between valuesof between about 10 pM and 100 pM (a low-affinity receptor having aconstant Kd situated between the values of between 2 nM and 10 nM).

Given the importance, at the medical level, of the fine understanding ofthe phenomena of regulation of IL-4 and of IL-13, and in particular ofthe possibility of being able to separate and control separately theeffects produced by either of these two cytokines, the authors of thepresent invention were interested on the one hand, in thecharacterization of a polypeptide specifically binding IL-13 with a highaffinity and, on the other hand, in the characterization of anotherpolypeptide which, alone, specifically binds IL-13 with a low affinityand which, if it is associated with the IL-4 receptor, constitutes ahigh-affinity receptor for IL-13.

These authors have now identified a human carcinoma cell line expressingthe IL-13 specific receptor in a quantity greater than other known humanrenal carcinoma lines (21), and have now carried out the cloning of theprimary subunit responsible for the attachment of IL-13 to theIL-4/IL-13 receptor, called IL-13Rβ, as well as the cloning of thecommon chain shared by the IL-13 receptor and the IL-4 receptor in orderto constitute a high-affinity receptor which allows cross-competitionbetween the 2 cytokines, called IL-13Rα. The present invention thereforerelates to purified polypeptides specifically linking IL-13.

More particularly, the subject of the invention is purified polypeptideswhose amino acid sequences correspond to that of a receptor specific forIL-13 (IL-13Rβ and IL-13Rα), or biologically active fragments thereof.

The subject of the invention is also isolated DNA sequences encoding thesaid polypeptides or their biologically active fragments.

It relates, in addition, to the expression vectors containing at leastone of the nucleotide sequences defined above, and the host cellstransfected with these expression vectors under conditions allowing thereplication and/or expression of one of the said nucleotide sequences.

The methods for producing recombinant IL-13Rβ and IL-13Rα or theirbiological active fragments by the transfected host cells are also partof the invention.

The invention also comprises pharmaceutical compositions comprisingIL-13Rβ and/or IL-13Rα or biologically active fragments thereof for theregulation of the immunological and inflammatory mechanisms produced byIL-13. It relates, in addition, to a method for the identification ofagents capable of modulating the activity of IL-13Rβ and/or IL-13Rα, andthe use of IL-R13β and/or IL-13Rα or of fragments thereof for screeningthese agents as well as for the manufacture of new products capable ofmodulating the activity of the IL-13 receptor.

The invention also comprises antibodies or derivatives of antibodiesspecific for IL-13Rβ and/or IL-13Rα.

Finally, it relates to a method of therapeutic treatment for modulatingthe immunological reactions mediated by IL-13, comprising theadministration, to a patient, of IL-13Rβ and/or IL-13Rα or of one oftheir biologically active fragments or of a compound capable ofspecifically modulating the activity of this receptor, in combinationwith a pharmaceutically acceptable vehicle.

In the description of the invention below, the following definitions areused:

-   polypeptide specifically binding IL-13 with a high affinity    (IL-13Rβ): a polypeptide comprising the amino acid sequence SEQ ID    No. 2 or any biologically active fragment or derivative thereof;-   polypeptide which, alone, specifically binds IL-13 with a low    affinity and which, if it is associated with the IL-4 receptor,    constitutes a high-affinity receptor (IL-13Rα): a polypeptide    comprising the amino acid sequence SEQ ID NO 4 or any biologically    active fragment or derivative thereof;-   biologically active: capable of binding specifically to IL-13 and/or    of participating in the transduction of the signal specifically    produced by IL-13 at the level of the cell membrane, and/or capable    of interacting with the receptor specific for IL-4 (IL-4R/gp 140) so    as to form a complex capable of binding IL-4 and IL-13, and/or which    is recognized by antibodies specific to the polypeptide of sequence    SEQ ID No. 2 and/or of sequence SEQ ID No. 4, and/or capable of    inducing antibodies which recognize the polypeptide of sequence SEQ    ID No. 2 and/or of sequence SEQ ID No. 4;-   derivative: any polypeptide which is a variant of the polypeptide of    sequence SEQ ID No. 2 and/or of sequence SEQ ID No. 4, or any    molecule resulting from a modification of a genetic and/or chemical    nature of the sequence SEQ ID No. 2 or of sequence SEQ ID No. 4,    that is to say which is obtained by mutation, deletion, addition,    substitution and/or chemical modification of one or of a limited    number of amino acids, as well as any isoform sequence, that is to    say a sequence which is identical to the sequence SEQ ID No. 2 or to    the sequence SEQ ID No. 4, to one of their fragments or to one of    their modified sequences, containing one or more amino acids in the    D enantiomer form, the said variant, modified or isoform sequences    having conserved at least one of the properties which make them    biologically active.

The subject of the present invention is a purified polypeptidecomprising an amino acid sequence chosen from:

-   a) the sequence SEQ ID No. 2 or the sequence SEQ ID No. 4,-   b) any biologically active sequence derived from SEQ ID No. 2 or SEQ    ID No. 4, according to the definition given above.

The manufacture of derivatives may have various objectives, including inparticular that of increasing the affinity of the receptor for IL-13,that of modulating the cross-competition between IL-13 and IL-4, that ofenhancing their levels of production, of increasing their resistance toproteases, of modifying their biological activity or of conferring newpharmaceutical and/or biological properties on them.

Among biologically active variants of the polypeptides as defined above,the fragments produced by alternate splicing of the transcripts(messenger RNAs) of the gene encoding one of the amino acid sequencesdescribed above are preferred.

In an advantageous variant, the 8 C-terminal amino acids of thepolypeptide of sequence SEQ ID No. 2 are substituted by the following 6amino acids: VRCVTL.

According to another advantageous aspect, the invention relates to asoluble form of IL-13Rβ, called IL-13Rβs, comprising especially theextracelluar domain of the polypeptide of sequence SEQ ID No. 2stretching up to residue 343 and preferably up to residue 337 as well asa soluble form of IL-13Rα, called IL-13Rαs, comprising especially theextracelluar domain of the polypeptide of sequence SEQ ID No. 4stretching up to residue 343 and preferably up to the residues between336 and 342.

The polypeptide which comprises the sequence SEQ ID No. 2 or thesequence SEQ ID No. 4 represents a specific embodiment of the invention.As will emerge in the examples, this polypeptide may be expressed at thesurface of human cells so as to form a functional IL-13 receptor and/orcombine with the IL-4 receptor so as to form, with the γ chain of theIL-2 receptor, the receptor complex common to IL-4 and IL-13.

The subject of the present invention is also an isolated nucleic acidsequence, chosen from:

-   a) the sequence SEQ ID No. 1,-   b) the sequence SEQ ID No. 3,-   c) the nucleic acid sequences capable of hybridizing to the sequence    SEQ ID No. 1 or to the sequence SEQ ID No. 3, or to their    complementary sequences and encoding polypeptides having an IL-13    receptor activity, or allowing the reconstitution of a receptor    having a high affinity for IL-13 and IL-4,-   d) the nucleic acid sequences derived from the sequences a) and b)    and c) because of the degeneracy of the genetic code.

More particularly, the subject of the invention is a sequence encodingthe soluble part of IL-13Rβ or of IL-13Rα and any variant produced byalternate splicing of the transcripts of IL-13Rβ or of IL-13Rα,conserving at least one of the biological properties described.

A preferred embodiment is represented by a nucleic acid sequencecomprising or consisting of the stretch of nucleotides stretching fromnucleotide No. 1 up to nucleotide 1081, and preferably up to nucleotide1063 on the sequence SEQ ID No. 1.

Another preferred embodiment is represented by a nucleic acid sequencecomprising or consisting of the stretch of nucleotides stretching fromnucleotide No. 1 up to nucleotide No. 1059, and preferably up to thenucleotides between numbers 1041 and 1056 on the sequence SEQ ID No. 3.

Advantageously, the nucleic acid sequence according to the invention isa sequence encoding a protein corresponding to the mature form ofIL-13Rβ or of IL-13Rα, this mature protein being the result of therelease of the signal peptide.

The various nucleotide sequences of the invention may be of artificialorigin or otherwise. They may be DNA or RNA sequences obtained byscreening sequence libraries by means of probes produced on the basis ofthe sequence SEQ ID No. 1 or of the sequence SEQ ID No. 3. Suchlibraries may be prepared by conventional molecular biology techniquesknown to persons skilled in the art.

The nucleotide sequences according to the invention may also be preparedby chemical synthesis or alternatively by a combination of methodsincluding chemical or enzymatic modification of sequences obtained byscreening of the libraries.

These nucleotide sequences allow the preparation of nucleotide probesencoding a polypeptide according to the invention or a biologicallyactive fragment thereof. The appropriate hybridization conditionscorrespond to the temperature and ionic strength conditions customarilyused by persons skilled in the art, preferably to temperature conditionsof between T_(m)−5° C. and T_(m)−30° C. and still more preferably, totemperature conditions between T_(m)−5° C. and T_(m)−10° C. (highstringency), T_(m) being the melting temperature, defined as thetemperature at which 50 % of the base-paired strands separate. Suchprobes are also part of the invention. They may be used as a IN VITROdiagnostic tool for the detection, by hybridization experiments, oftranscripts specific for the polypeptides of the invention in biologicalsamples or for the detection of aberrant syntheses or of geneticabnormalities resulting from a polymorphism, from mutations or from apoor splicing.

The probes of the invention comprise at least 10 nucleotides, andcomprise at most the entire nucleotide sequence SEQ ID No. 1 or theentire nucleotide sequence SEQ ID No. 3 or their complementary strand.

Among the shortest probes, that is to say of about 10 to 15 nucleotides,the appropriate hybridization conditions correspond to the temperatureand ionic strength conditions customarily used by persons skilled in theart.

Preferably, the probes of the invention are labelled prior to their use.For that, several techniques are within the capability of personsskilled in the art, such as for example fluorescent, radioactive,chemiluminescent or enzymatic labelling.

The IN VITRO diagnostic methods in which these nucleotide probes areused for the detection of aberrant syntheses or of geneticabnormalities, such as the loss of heterozygosity and geneticrearrangement, at the level of the nucleic sequences encoding an IL-13receptor polypeptide or a biologically active fragment, are included inthe present invention. Such a type of method comprises:

-   bringing a nucleotide probe of the invention into contact with a    biological sample under conditions allowing the formation of a    hybridization complex between the said probe and the above-mentioned    nucleotide sequence, optionally after a preliminary step of    amplification of the abovementioned nucleotide sequence;-   detection of the hybridization complex which may be formed;-   optionally, sequencing the nucleotide sequence forming the    hybridization complex with the probe of the invention.

The cDNA probes of the invention may, in addition, be advantageouslyused for the detection of chromosomal abnormalities.

The nucleotide sequences of the invention are also useful for themanufacture and the use of sense and/or antisense oligonucleotideprimers for sequencing reactions or for specific amplification reactionsaccording to the so-called PCR (polymerase chain reaction) technique orany other variant thereof.

The nucleotide sequences according to the invention have, moreover, usesin the therapeutic field for the preparation of antisense sequenceswhich are capable of hybridizing specifically with a nucleic acidsequence, including a messenger RNA, and may be used in gene therapy.The subject of the invention is thus antisense sequences capable ofinhibiting, at least partially, the production of IL-13 receptorpolypeptides as defined above. Such sequences advantageously consist ofthose which constitute the reading frame encoding IL-13Rβ or IL-13Rα atthe level of the transcript.

They may be more particularly used in the treatment of allergies and ofinflammation.

The nucleotide sequences according to the invention may, moreover, beused for the production of recombinant polypeptides, as defined above,having an IL-13 receptor activity.

These polypeptides may be produced from the nucleotide sequences definedabove, according to techniques for the production of recombinantproducts known to persons skilled in the art. In this case, thenucleotide sequence used is placed under the control of signals allowingits expression in a cellular host. The cellular host used may be chosenfrom prokaryotic systems, such as bacteria, or from eukaryotic systems,such as yeasts, insect cells, CHO cells (chinese hamster ovary cells) orany other system which is advantageously available commercially. Acellular host preferred for the expression of the polypeptides of theinvention consists of the fibroblast line COS-7 or COS-3.

The signals controlling the expression of the polypeptides, such as thepromoters, the activators or the terminal sequences, are chosenaccording to the cellular host used. To this end, the nucleotidesequences according to the invention may be inserted into autonomouslyreplicating vectors within the chosen host, or integrative vectors ofthe chosen host. Such vectors will be prepared according to the methodscommonly used by persons skilled in the art, and the resulting clonesmay be introduced into an appropriate host by standard methods, such asfor example electroporation.

The expression vectors containing at least one of the nucleotidesequences defined above are also part of the present invention.

In the case of the COS-7 or COS-3 cells, the transfection may be carriedout using the vector pSE-1, as described in (17).

The invention relates, in addition, to the host cells transfected bythese expression vectors. These cells may be obtained by theintroduction, into host cells, of a nucleotide sequence inserted into avector as defined above, followed by the culture of the said cells underconditions allowing the replication and/or expression of the transfectednucleotide sequence.

These cells may be used in a method for the production of a recombinantpolypeptide of sequence SEQ ID No. 2 or SEQ ID No. 4 or a derivative,which method is itself included in the present invention and ischaracterized in that the transfected cells are cultured underconditions allowing the expression of a recombinant polypeptide ofsequence SEQ ID No. 2 or SEQ ID No. 4, or a derivative, and in that thesaid recombinant polypeptide is recovered.

The purification processes used are known to persons skilled in the art.The recombinant polypeptide may be purified from cell lysates andextracts, from the culture supernatant, by methods used individually orin combination, such as fractionation, chromatographic methods,immunoaffinity techniques using specific mono- or polyclonal antibodies.

The mono- or polyclonal antibodies capable of specifically recognizingIL-13Rβ and/or IL-13Rα according to the definition given above are alsopart of the invention. Polyclonal antibodies may be obtained from theserum of an animal immunized against IL-13Rβ and/or IL-13Rα according tothe usual procedures.

The monoclonal antibodies may be obtained according to the conventionalhybridoma culture method described by Köhler and Milstein (Nature, 1975,256, 495-497).

Advantageous antibodies are antibodies directed against the extracelluardomain of IL-13Rβ and/or IL-13Rα.

The antibodies according to the invention are, for example, chimericantibodies, humanized antibodies, Fab and F(ab′)2 fragments. They mayalso exist in the form of labelled antibodies or immunoconjugates. Forexample, they may be associated with a toxin, such as the diphtheriatoxin or with a radioactive product. These immunotoxins may in this caseconstitute therapeutic agents which may be used for the treatment ofcertain pathologies involving an overexpression of IL-13Rβ and/orIL-13Rα.

The antibodies of the invention, in particular the monoclonalantibodies, may also be used for the immunocytochemical analyses of theIL-13 receptors on specific tissue sections, for example byimmunofluorescence or by gold or peroxidase labelling.

They may be advantageously used in any situation where the expression ofIL-13Rβ and/or IL-13Rα needs to be observed, such as for example anabnormal over-expression or the monitoring of the regulation of membraneexpression.

The invention therefore also relates to a process for the IN VITROdiagnosis of pathologies correlated with an abnormal expression ofIL-13Rβ and/or of IL-13Rα, in biological samples capable of containingIL-13Rβ and/or IL-13Rα expressed at an abnormal level, characterized inthat at least one antibody of the invention is brought into contact withthe said biological sample, under conditions allowing the possibleformation of specific immunological complexes between IL-13Rβ and/or ofIL-13Rα and the said antibody(ies) and in that the specificimmunological complexes which may be formed are detected.

The invention also relates to a kit for the IN VITRO diagnosis of anabnormal expression of IL-13Rβ and/or of IL-13Rα in a biological sampleand/or for measuring the level of expression of the IL-13 receptor inthe said sample comprising:

-   at least one antibody specific for IL-13Rβ and/or IL-13Rα,    optionally attached onto a support,-   means for revealing the formation of specific antigen/antibody    complexes between IL-13Rβ and/or IL-13Rα and the said antibody(ies)    and/or means for quantifying these complexes.

Another subject of the invention relates to a method for theidentification and/or isolation of ligands specific for IL-13Rβ and/orIL-13Rα or agents capable of modulating its activity, characterized inthat a compound or a mixture containing various compounds, optionallynonidentified, is brought into contact with cells expressing at theirsurface IL-13Rβ and/or IL-13Rα, under conditions allowing interactionbetween the IL-13 receptor and the said compound, in the case where thelatter would have an affinity for the receptor, and in that thecompounds bound to IL-13Rβ and/or IL-13Rα, or those capable ofmodulating the biological activity thereof, are detected and/orisolated.

In a specific embodiment, this method of the invention is adapted to theidentification and/or isolation of agonists and of antagonists of IL-13for its IL-13Rβ and/or IL-13Rα receptor.

The invention also comprises pharmaceutical compositions comprising, asactive ingredient, a polypeptide corresponding to the precedingdefinitions, preferably in a soluble form, combined with apharmaceutically acceptable vehicle.

Such a polypeptide may indeed act in competition with IL-13Rβ and/orIL-13Rα expressed at the cell surface, and thereby constitute anantagonist specific for the binding of IL-13 to its receptor, which maybe advantageously used for the synthesis of a medicinal product intendedfor modulating the reactions mediated by IL-13 in pathologicalsituations.

Finally, the invention comprises a method for the therapeutic treatmentof conditions linked to immunological reactions mediated by IL-13,comprising the administration to a patient of IL-13Rβ and/or IL-13Rα (orof one of their biologically active fragments), or of a compound capableof specifically modulating the biological activity thereof, incombination with a pharmaceutically acceptable vehicle.

Other characteristics and advantages of the invention will emerge in therest of the description with the examples and the figures, of which thelegends are represented below.

LEGEND TO THE FIGURES

FIG. 1: characterization of the human IL-13Rβ receptor present in Caki-1cells.

-   a) Scatchard analysis (inset) of the saturation curve of IL-13    labelled with [¹²⁵I];-   b) binding of [¹²⁵I] [Phe43]-IL-13-GlyTyrGlyTyr in the presence of    increasing concentrations of unlabelled IL-13 (•) and of IL-4 (o);-   c) cross-linking experiments using radioactive IL-13 in the absence    (lane a) and in the presence of a one hundred times excess of    unlabelled IL-13 (lane b) or of IL-4 (lane c);-   d) inhibition of the secretion of IL-6 induced by IL-13 and IL-4 in    the presence of a monoclonal antibody specific for the IL-4R chain    and the IL-4 antagonist Y124DIL-4.

FIG. 2: Nucleotide sequence of the cDNA of IL-13Rβ, and comparison ofthe protein sequences of IL-5R and IL-13Rβ.

-   a) nucleotide sequence of the cDNA of IL-13Rβ. The amino acids    corresponding to the deduced signal peptide of the nucleic sequence    are indicated in italics and those corresponding to the    transmembrane domain are indicated in bold characters. The potential    N-glycosylation sites (Asn-X-Ser/Thr) are underlined;-   b) alignment of the amino acids of the IL-13Rβ and IL-5R sequences.    The protein sequences of IL-13R and IL-5R are aligned as described    above (24). The cysteine residues and the WSXWS motif which are    characteristic of this family of receptors are boxed.

FIG. 3: patterns of expression of the IL-13Rβ mRNA.

The RNA was prepared from the following cells: Caki-1 (lane a), A431(lane b), TF-1 (lane c), U937 (lane d), Jurkat (line e) and IM9 (lanef).

FIG. 4: characterization of the recombinant IL-13Rβ receptor for IL-13.The COS-7 cells are transfected with IL-13Rβ cDNA and used for:

-   a) studies for the binding of radiolabelled IL-13 (inset) by    Scatchard analysis of the saturation curve;-   b) cross-linking experiments using radiolabelled IL-13 in the    absence (lane a) and in the presence of a one hundred times excess    of unlabelled IL-13 (lane b);-   c-d) cotransfection experiments using cloned IL-13Rβ, IL-4R (gp140)    and the γc chain followed by the binding of radiolabelled IL-13 (c)    or of IL-4 (d). The black and white columns represent the specific    binding of IL-13 and of IL-4 respectively.

FIG. 5: inhibition of the binding of IL-13 to IL-13Rβ by the solubleform of the receptor (IL-13Rβs) in transient expression.

The expression of IL-13Rβs in the supernatant of the cells transfectedwith 2034 is tested by inhibition of the binding of IL-13 on cellstransfected with IL-13Rβ (2036). The supernatants are tested in thecrude state by diluting them one half in the iodinated ligand.

-   2036 NSB: nonspecific binding in the presence of an excess of    unlabelled IL-13.-   2036 BT: total binding on cells transfected with 2036-   2036+sgt 2034: binding to cells transfected with 2036 in the    presence of supernatant of cells transfected with 2034.-   2036+sgt pSE1: control

FIG. 6: inhibition of the binding of IL-13 to IL-13Rβ by the solubleform of the receptor (IL-13Rβs) on stable lines.

-   T2036-22: total binding on the clone IL-13Rβ (2036-22) in the    absence of supernatant of clone secreting IL-13Rβs (reference 100%)-   2034-4-   2034-6-   2034-19 4 clones IL-13Rβs-   2034-21-   1274-20: in the presence of supernatant of CHO cells not expressing    IL-13Rβs (control).

FIG. 7: nucleotide sequence of the IL-13Rα cDNA and comparison of theprotein sequences of human IL-13Rα and of murine IL-13Rα.

-   a) Nucleotide sequence of the IL-13Rα cDNA. The amino acids    corresponding to the signal peptide deduced from the nucleic    sequence are underlined with a dotted line and those corresponding    to the transmembrane domain are underlined with a double line. The    potential N-glycosylation sites (Asn-X-Ser/Thr) are boxed.-   b) Alignment of the amino acids of human IL-13Rα and of murine    IL-13Rα. The protein sequences of human IL-13Rα and of murine    IL-13Rα are aligned as described above (24). The cysteine residues    and the motif WSXWS which are characteristic of this family of    receptors are boxed.

FIG. 8: characterization of the recombinant IL-13Rα receptor for IL-13.

The CHO or COS-3 cells transfected with the IL-13Rα and/or IL-4R cDNAand used for:

-   a) studies of the binding of iodine-125 labelled IL-13 by Scatchard    analysis of the saturation curve with CHO cells transfected with    IL-13Rβ cDNA (Figure A), transfected with IL-13Rβ cDNA and IL-4R    cDNA (Figure B), transfected with IL-13Rα cDNA (Figure C) and    transfected with IL-13Rα cDNA and IL-4R cDNA (Figure D),-   b) competition experiments of binding of [¹²⁵I]-IL-13 on CHO cells    transfected with IL-13Rβ cDNA (Figure E), transfected with IL-13Rβ    cDNA and IL-4R cDNA (Figure F), transfected with IL-13Rα cDNA    (Figure G) and transfected with IL-13Rα cDNA and IL-4R cDNA (Figure    H). The white and shaded columns represent respectively the specific    binding of radiolabelled IL-13 in the presence of an excess (1,000    times more) of IL-13 or IL-4, the black columns represent total    binding.

FIG. 9: comparison of the electrophoretic mobility in EMSA of cellularextracts expressing the receptor for IL-4 alone (CHO-4), the receptorfor IL-13Rα alone (CHO-13) or the combined receptors IL-13Rα and IL-4R(CHO-4-13) after activation of the CHO cells in the presence of IL-4 orIL-13 (4 or 13), c representing the nonactivated control.

MATERIALS AND METHODS

Binding and Cross-Linking Experiments:

The binding and cross-linking experiments are carried out as describedfor [¹²⁵I] [Phe43]-IL-13-GlyTyrGlyTyr (17).

Induction of the Secretion of IL-6:

The Caki-1 cells (ATCC HTB46) are placed in 24-well plates at a densityof 5×10⁴ cells/well and after 3 days of culture, confluent monolayersare washed three times with DMEM medium without foetal calf serum. Thestimulation of the Caki-1 cells is carried out with 30 ng/ml of IL-4 orof IL-13 in the absence or in the presence of Y124DIL-4 or of ananti-gp140 monoclonal antibody. The quantity of IL-6 released into theculture medium after incubating for 24 hours is measured by an ELISAtechnique (Innotest, France).

Isolation and Analysis of the Human IL-13Rβ cDNA:

Total RNA was extracted from the Caki-1 cells as described above (25).The poly(A) RNA is isolated from the total RNAs with magnetic beadscoated with oligo(dT)₂₅ (Dynal). A cDNA library containing 2×10⁵ cloneswas constructed using the primer-adaptor procedure (26) and the vectorpSE-1 (27). The cloning strategy for the expression which was used hasbeen previously described (17).

PreDaration of Human IL-13Rβ cDNA:

The RNA samples are copied with reverse transcriptase and subjected toPCR (polymerase chain reaction) using a sense primer corresponding tothe sequence +52 to +71 and an antisense primer corresponding to +489 to470 (the numbering is made on the basis of the cDNA sequence shown inFIG. 2). The PCR-amplified products are hybridized with a probecomplementary to sequences +445 to +461 of the cDNA. The size markersare indicated on the left of the figure.

Isolation and Analysis of the Human IL-13Rα cDNA:

1) Preparation of the Murine IL-13Rα Probe

a) Culture of the B9 Cells (28)

The B9 cells are cultured in RPMI medium (Gibco) supplemented with 10%foetal calf serum and 50 μg/ml of gentamycin.

b) Preparation of the RNA of the B9 Cells.

The cells are washed twice with PBS buffer (phosphate buffered saline,reference 04104040-GIBCO-BRL). After centrifugation for 10 min at 1000rpm, the cellular pellet is suspended in the lysis buffer of thefollowing composition: 4M guanidine-thiocyanate; 25 mM sodium citrate pH7; 0.5% sarcosyl; 0.1 M β2-mercapto-ethanol.

The suspension is sonicated using an Ultraturax sonicator No. 231256(JANKE and KUNDEL) at the maximum power for one minute. Sodium acetatepH 4 is added to 0.2 M. The solution is extracted with one volume of aphenol/chloroform mixture (v/v: 5/1).

The RNA contained in the aqueous phase is precipitated at −20° C. withthe aid of one volume of isopropanol. The pellet is resuspended in thelysis buffer. The solution is again extracted with a phenol/chloroformmixture and the RNA is precipitated with isopropanol. After washing thepellet with 70% and then 100% ethanol, the RNA is resuspended in water.

c) Preparation of the Complementary DNA.

The cDNA is prepared from 5 μg of total RNA using a poly T12 primer. Thetotal RNA is incubated in a volume of 30 μl of buffer: 50 mM Tris-HCl pH8.3, 6 mM MgCl₂, 10 mM DTT, 40 mM KCl, containing 0.5 mM of each of thedeoxynucleotide triphosphates and 30 units of Rnasin (Promega), for onehour at 37° C., and then for 10 minutes at 50° C., and then for afurther 10 minutes at 37° C., with 200 units of the reverse transciptazeenzyme Rnase H (Gibco-BRL reference 8064A). The reaction is stopped byheating for 10 minutes at 65° C.

d) Specific Amplification of a Mouse IL-13Rα cDNA Fragment by the PCRTechnique.

The polymerization is carried out with 6 μl of cDNA in 50 μl finalvolume with the buffer of the following composition: 10 mM Tris-HCl pH8.3, 2.5 mM MgCl₂, 50 mM KCl, 4 dNTP 0.2 mM, 2 μg/ml of each of the twonucleic primers and 2.5 U of TAQ DNA polymerase (Beckman). The pairs ofprimers were chosen on the sequence published by Hilton (22).

Sense primer: nucleotide 249 to 268

5′ AGAGGAATTACCCCTGGATG 3′

Antisense primer: nucleotide 1256 to 1275

5′ TCAAGGAGCTGCTTTCTTCA 3′

The reaction is carried out for 30 cycles of 1 minute at 94° C., 1minute at 58° C., 4 minutes at 72° C., followed by a final cycle of 10minutes at 72° C.

e) Purification of the PCR Amplification Product.

After running on a 1% agarose gel (Sigma) in TAE buffer (40 mM,Tris-HCl, 1 mM EDTA pH 7.9) for 1 hour at 100 volts, the gel is stainedin the presence of 1 μg/ml of ethidium bromide in the same buffer. Theband corresponding to the amplification product (cDNA fragment of 1027base pairs (bp) of IL-13Rα) is extracted using a Glass Max kit (Gibco).

f) Preparation of the Probe.

25 ng of the purified cDNA fragment of 1027 bp corresponding to themouse IL-13Rα receptor are labelled with phosphorus-32 with the BRLRandom Primers DNA labelling systems kit at a specific activity of2.4×10⁹ dpm/μg; alternatively, 100 ng are labelled by nick translationusing the Boeringher kit at a specific activity of 4×10⁸ dpm/μg.

2) Isolation and Analysis of the Human IL-13Rα cDNA

a) Preparation of the Total RNA

The total RNA was extracted from Caki-1 cells as described above inparagraph 1b.

b) Purification of the Messenger RNA (PolyA+ fraction)

The purification of the polyA+ fraction of the RNA is carried out usingthe DYNAL oligo (dT)₂₅ Dynabeads kit (reference 610.05) following theprocedure recommended by the manufacturer. The principle is based on theuse of superparamagnetic polystyrene beads onto which a poly(dT)₂₅oligonucleotide is attached. The polyA+ fraction is hybridized with theoligo(dT)₂₅ oligonucleotide coupled to the beads which are trapped on amagnetic support.

c) Northern Blot.

5 μg of polyA+ messenger RNA are loaded on a 1% agarose, 8% formaldehydedenaturing gel in MOPS buffer (10 mM pH 7.4, 0.5 mM EDTA). Aftermigration and transfer onto an N+ Hybond membrane (Amersham) in a 20×SSCbuffer, the RNA is fixed by heating in an oven at 80° C. under vacuum.The membrane is then prehybridized for 2 hours at 42° C. in thefollowing buffer: 1 M NaCl, 30% formamide; 1% SDS, 5× Denhart's; 100μg/ml of salmon sperm DNA. After 2 hours of prehybridization, themembrane is hybridized in the same buffer with a concentration of mouseIL-13Rα probe prepared by random priming of 2.5×10⁶ dpm/ml, for 16hours. The membrane is then washed twice for 30 minutes in 2×SSC buffer0.1% SDS at room temperature for 2 hours at 50° C. in the same buffer.After 4 days of exposure in a cassette (Molecular Dynamics), theNorthern blot is analysed with an Instant Imager (Molecular Dynamics). Apredominant transcript of 4200 bp and a doublet of 1500 bp and 2000 bpare detected in the Caki-1 cells, U373 and U937.

Characterization of the Properties of the Human IL-13Rα and IL-13Rβ:

The COS-7 or CHO cells are transfected in Petri dishes as describedabove (17). 24 hours later, the cells are trypsinized and cultured in24-well plates at a density of 8×10⁴ cells/well. After culturing for 48hours at 37° C., the cells are used for the binding experiments (assayscarried out in triplicate show a variation of less than 10%) withiodinated IL-13 as described (17). For the transfection, the COS-7 orCHO cells were transfected in 25-cm² plates using 0.6 mg of variousplasmids. After 24 hours, the cell monolayers are trypsinized andcultured in 12-well plates at 8×10⁴ cells/well. Three days later, thebinding and competition experiments are carried out with labelled IL-13and with unlabelled IL-13 and/or IL-4. The results are representative ofat least three experiments conducted independently.

Comparison of Electrophoretic Mobilities in EMSA of the Nuclear Extractsof the Cells Expressing the Human IL-13Rα and/or IL-4R:

2×10⁶ CHO cells are plated onto 10 cm Petri dishes. 24 hours later, thecells are transfected with 6 μg of plasmid DNA (34). After 48 hours, thecells are incubated at 37° C. for 30 minutes in 3 ml of medium with orwithout IL-13 or IL-4 at a concentration of 100 ng per ml. The cells arethen rinsed twice with a PBS-0.5 mM EDTA buffer and then harvested in1.2 ml of PBS. The cells are then centrifuged and the cellular extractsprepared as described in (35). The EMSAs are then carried out asdescribed in (36) with 10 to 20 μg of cellular extracts and with anoligonucleotide probe radiolabelled with ³²P (50,000-100,000 cpm), aprobe corresponding to the Cε element of the human Cε promoter (37). Theoligonucleotide probe synthesized has the following sequence:5′-GATCCACTTCCCAAGAACAGA-3′.

EXAMPLES Example 1 Analysis of the Expression of Human IL-13Rβ at theSurface of Caki-1 Cells

It was recently discovered that human renal carcinoma cells expressed,in addition to the receptors shared by IL-4 and IL-13, a large excess ofspecific IL-13 receptors (21). On the basis of these results, a sampleof human carcinoma cell lines was studied for the attachment of IL-13 asdescribed above (17). A specific line, Caki-1 (ATCC HTB46), whichexpresses a particularly large number of binding sites for IL-13, wasanalysed in greater detail. The Scatchard curves obtained fromsaturation experiments show the presence of binding sites with a Kd of446±50 pM and a capacity of 7.2×10⁴ receptors/cell (FIG. 1 a). Incompetition experiments, unlabelled IL-13 completely displaces labelledIL-13 in a dose-dependent manner, whereas IL-4 displaces with a highaffinity about 10% of the labelled IL-13. Higher concentrations of IL-4(greater than 100 nM) do not displace the remaining 90% of bound IL-13(FIG. 1 b).

These results are in agreement with the existence of two sites, oneshared by the two cytokines, the other specific for IL-13. Theexperiments on cross-linking by affinity for IL-13 show a complex ofabout 70 kDa, which coincides with the complex observed in similarcross-linking experiments with IL-13 in various cell types (17, 21).Labelled IL-13 is completely displaced from the complex by IL-13 but notby IL-4, which is in agreement with the competition experiments (FIG. 1c).

Example 2 Analysis of the Secretion of IL-6 Induced by IL-4 or IL-13

The authors of the invention analysed the secretion induced by IL-4 orIL-13 on Caki-1 cells. The two cytokines induce the secretion of similarlevels of IL-6, and the secretion is inhibited by antibodies specificfor the α chain of IL-4R and by the antagonist Y124DIL-4 (FIG. 1 d).This suggests that the receptors shared by the two cytokines in theCaki-1 cells are responsible for the induction of the secretion of IL-6.Similar results are observed when the phosphorylation of the proteincomplex IRS1/4PS (18) induced by IL-4 and IL-13 is analysed in thepresence or in the absence of anti-IL-4R antibodies and of IL-4antagonist.

These results, taken as a whole, suggest that the receptor complexIL-4/IL-13 expressed in the Caki cells is identical to that which waspreviously described and that the protein binding IL-13 (IL-13Rβ) whichis over-expressed is a component of the receptor responsible for therecognition of IL-13 in a functional complex which includes IL-4R. Thesecells were therefore used as source of messenger RNA for the cloning ofthis IL-13 binding entity.

Example 3 Cloning of the Primary Unit of the IL-13 Receptor (IL-13Rβ)

The strategy for the cloning and expression which was used has beenpreviously described (17). A cDNA library containing 2×10⁵ recombinantclones was constructed (26) using Caki-1 cells. The library was dividedinto batches of 1000 cDNAs in which the DNA of each batch, in plasmidform, was introduced into COS-7 cells (29). The binding of labelledIL-13 to the transfected COS-7 cells makes it possible to identify thebatches of clones encoding an IL-13 receptor. The positive batches weredistributed out and rescreened until a single clone capable of carryingout the synthesis of a cell surface protein capable of binding IL-13 isidentified. Two independent IL-13Rβ cDNAs were finally isolated. Thecomplete nucleotide sequence of the IL-13Rβ cDNA and the amino acidsequence deduced therefrom are shown in FIG. 2 a. The cDNA has a lengthof 1298 bases excluding the poly-A tail and has a short 3′ untranslatedregion of 106 bases. A canonical AATAAA polyadenylation signal is in theexpected place. The open reading frame between nucleotides 53 and 1192defines a polypeptide of 380 amino acids. The sequence encodes amembrane protein with a potential signal peptide, a single transmembranedomain and a short intracytoplasmic tail.

Four potential N-glycosylation sites are located in the extracelluarregion. It is important to note that two consensus motifs considered assignatures of the type II family of cytokine receptors (30) are alsopresent, the first being derived from an N-terminal disulphide bridgeloop structure, the second being the WSXWS type motif located at theC-terminal end of the extracellular region. The very short cytoplasmicsequence might explain why it is only the receptor complex shared byIL-4 and by IL-13 in the Caki cells which transduces a signal in thecell.

Alignment studies demonstrate homologies with the human IL-5R α chain(51% similarity and 27% identity, FIG. 2 b) and, to a lesser extent,with the prolactin receptor. It is interesting to note that the IL-5Rcomplex consists of an α chain which binds IL-5 but which needs anotherprotein, the β chain shared with the IL-3 and GM-CSF receptors, to forma high-affinity receptor which is capable of transducing a signal (31).

Example 4 Detection of the Human IL-13Rβ Messenger RNAs in Various CellLines

Surprisingly, in the Caki-1 cells, similar quantities of messenger RNAsfor IL-13Rβ and IL-4R are detected by Northern analyses although a largeexcess of IL-13Rβ is expressed. This observation suggests that there isa greater translation of this mRNA compared with the IL-4R transcriptand explains the lack of detection of the IL-13Rβ mRNA in the cell linesexpressing a small number of IL-13 binding sites. RT-PCR analyses (FIG.3) show that the transcript found in the Caki-1 cells is also present atlower levels in the keratinocytic line A431, the premyeloid cells TF-1,the premocytic cells U937 and the cell line B IM9. No transcript wasdetected in the Jurkat T cell line or in the pre-B NALM6 cell line.These results are in agreement with the IL-13 binding studies on thesesame lines previously described by the authors of the present invention(17), and with the known biological targets of IL-13.

Example 5 Binding Analyses Carried Out on COS-7 Cells Transfected withHuman IL-13Rβ cDNA

The COS-7 cells transfected with the isolated cDNA encoding IL-13Rβspecifically bind labelled IL-13. The Scatchard analysis of thesaturation curve shows a single component site with a Kd value of 250±30pM and a maximum binding capacity of 5.6×10⁵ receptors/cell (FIG. 4 a).

The affinity of the recombinant receptor is in good agreement with theKd value of 446 pM for IL-13Rβ in the Caki-1 cells and for what has beendescribed in several other cells (17). Consequently, in spite of asequence homology with the α chain of IL-5R, the cloned receptor behavesdifferently since it does not need a second chain to reconstitute a highaffinity binding site.

It is interesting to note that the protein binding IL-15 recentlydescribed likewise has the characteristic of binding IL-15 with a highaffinity, in the absence of the other two components of the IL-15Rcomplex (32).

In competition experiments, IL-13 is capable of inhibiting the bindingof labelled IL-13 to the cloned receptor, with an inhibitory constant(Ki) of 1.5±0.5 nM, whereas IL-4 does not inhibit the binding. Thepharmacology of the cloned receptor is therefore similar to that of theIL-13Rβ present in Caki-1 cells. Cross-linking experiments show aradiolabelled band of 70 kDa. This band has the same mobility as thatobserved in the Caki cells as well as in other cells (17). This complexmost probably corresponds to the 60-70 kDa band observed in addition tothe IL-4R 140 kDa band in cross-linking experiments carried out withlabelled IL-4. This could also suggest that a strong interaction existsbetween the two proteins in the functional receptor complex. The authorsof the present invention therefore checked if IL-13Rβ and IL-4R interactin the cell membrane to reconstitute a receptor which allowscross-competition between the two cytokines. The results of acoexpression experiment are shown in FIGS. 4 c and d.

It appears clearly that the expression of the two receptors, eitherseparately or simultaneously, results in a large number of receptorswhich specifically recognize either of the two cytokines. However, whenthey are expressed together, a small number of receptors (5 to 10%) iscapable of recognizing the two cytokines. The cotransfection of the γcchain with IL-4R and IL-13Rβ does not bring about an increase in thenumber of shared binding sites. These results suggest that the IL-13Rβand IL-4R chains can interact with each other in the cell membrane toreconstitute a receptor for which IL-13 and IL-4 may be in competition.The low percentage of reconstituted receptors is an argument in favourof the presence of another protein (IL-13Rα) in limiting amounts in theCOS cells which is necessary for the reconstitution of the receptorcomplex to which IL-13 and IL-4 bind competitively.

The results obtained in the transfection experiments with the γc chaindemonstrate that this protein is not the limiting factor which waspreviously suggested (15). This conclusion is also supported by theabsence of γc messenger RNA in the Caki-1 cells (21).

Another possible reason which explains the low number of reconstitutedreceptors is the existence of an incorrect stoichiometry of the twoproteins in the cell membrane. However, cotransfections using differentrelative quantities of IL-4R and IL-13Rβ do not show a major differencein the number of reconstituted receptors. The possibility that anotherIL-13R with a greater capacity to interact with IL-4R exists wasconfirmed in mice (22) and in man by the isolation of the IL-13Rα cDNA(cf. EXAMPLE 7). It should be noted that the expression of γc enhancesthe binding of IL-4 as previously described (19) but reduces the bindingof IL-13, suggesting a complex interaction between the different chains.

Example 6 Study of the Inhibition of the Binding of IL-13 to ItsMembrane Receptor by a Receptor in Soluble Form

The results in transient expression (FIG. 5) or on stable lines (FIG. 6)are described.

The two cDNA sequences encoding IL-13Rβ and IL-13Rβs are inserted intothe vector p7055 in place of the IL-2 cDNA (33). The resulting plasmidsare called 2036 and 2034 respectively.

a) Transient Expression

The CHO cells are inoculated into 12-well plates at 3×10⁵ cells/well andtransfected the next day by the DEAE-Dextran method as for the COScells, either with the plasmid 2036 or 2034, or with the empty plasmidpSE-1 as control.

The cells are cultured for three days so as to allow accumulation ofIL-13Rβs in the supernatant of the cells transfected with the plasmid2034 and good expression of IL-13Rβ in the membrane of the cellstransfected with the plasmid 2036.

The supernatant of the cells transfected with IL-13Rβs (2034) or thenegative control (empty pSE-1) is then collected and the cellstransfected with IL-13Rβ are used to study the inhibition of the bindingof IL-13.

The binding of IL-13 to the surface of the CHO cells expressing IL-13Rβ(2036) is measured in the presence or otherwise of these crudesupernatants diluted one half with the radioligand or in the presence ofan excess of nonradiolabelled IL-13 (NSB). The binding is carried out onwhole cells in a final volume of 500 ml with 300 pM of radioligand, intriplicate.

b) Stable Lines

Two stable transformed CHO lines are obtained by transfection with thecoding sequences of the complete IL-13Rβ (polypeptide of 380 residues)or of the IL-13Rβ in soluble form (IL-13Rβs, truncated polypeptidecorresponding to residues 1 to 337 of IL-13Rβ). These sequences areinserted into the vector p7055.

The CHO-DHFR⁻ cells are transfected with the plasmids 2036 (IL-13Rβ) and2034 (IL-13Rβs) and the recombinant clones selected as previouslydescribed (33).

One of the clones CHO-IL-13Rβ (CHO 2036) obtained, having 2 to 5×10⁵sites per cell, is inoculated into a 12-well plate at a density of 10⁵cells per well and the cells are used two days later for bindingexperiments in the presence or otherwise of IL-13Rβs.

For that, the CHO-IL-13Rβs (CHO 2034) clones are inoculated into 6 cmdishes, in triplicate, at 5×10⁵ cells per dish. After 3 days ofaccumulation in the culture medium, the medium (5 ml per dish) iscollected for the IL-13 binding inhibition studies on IL-13Rβ of the CHO2036 clone. In the same manner, the supernatant of CHO cells notexpressing the soluble IL-13Rβ is collected.

The binding of IL-13 at the surface of the CHO 2036-22 clone is measuredin the presence or otherwise of these crude supernatants diluted onehalf with the radioligand, or in the presence of an excess ofnonradiolabelled IL-13 (NSB). The binding is carried out in triplicate,on whole cells, in a volume of 500 ml with 300 pM of radioligand.

The histograms of FIGS. 5 and 6 represent the inhibition of the bindingof IL-13 on IL-13Rβ by IL-13Rβs. Inhibition of the binding of IL-13 toits receptor can be observed on several clones.

Example 7 Cloning of the Human IL-13Rα Receptor

a) Preparation of the cDNA Library from PolyA+ Messenger RNAs of Caki-1Cells

Starting with 0.5 μg of polyA+ messenger RNA, single-strandedcomplementary DNA labelled with [³²P]dCTP (the complementary DNAobtained has a specific activity of 3000 dpm/ng) is prepared with thesynthetic primer having the following sequence (comprising a BamHIsite): 5′ <GATCCGGGCCCTTTTTTTTTTTT <3′ (SEQ ID NO. 10)in a volume of 30 μl of the following buffer: 50 mM Tris-HCl pH 8.3, 6mM MgCl₂, 10 mM DTT, 40 mM KCl, containing 0.5 mM of each of thedeoxynucleic triphosphates, 30 μCi of [α³²P]dCTP and 30 U of Rnasin(Promega). After incubating for 1 hour at 37° C., and then for 10minutes at 50° C. and then for a further 10 minutes at 37° C., with 200units of the reverse transcriptase enzyme Rnase H (Gibco-BRL), 4 μl ofEDTA are added. The RNA template is then degraded by adding 6 μl of a 2N NaOH solution and incubating for 5 minutes at 65° C.

To remove the synthetic primer, the complementary DNA is purified on a 1ml Sephacryl S400 column (Pharmacia), equilibrated in TE buffer. Thefirst two radioactive fractions are combined and precipitated with a1/10 volume of a 10 M ammonium acetate solution and 2.5 volumes ofethanol, this after extraction with chloroform. The cDNA is thenextended in 5′ by adding a dG homopolymeric tail with 20 units ofterminal transferase enzyme (Pharmacia 27073001). Next, incubation isperformed in 20 μl of buffer having the following composition: 30 mMTris-HCl pH 7.6: 1 mM cobalt chloride; 140 mM cacodylic acid; 0.1 mMDTT; 1 mM dGTP, for 15 minutes at 37° C., and then 2 μl of 0.5 M EDTAare added. A further treatment with sodium hydroxide is carried outwithout heating, followed by repurification on an S400 column,extraction with chloroform and precipitation with ethanol. The pellet isdissolved in 33 μl of TE buffer. The next stage consists in pairing thecloning vector pT7T3-18 through which a homopolymeric dC tail has beenadded beforehand after cutting with Pst1, the cDNA and the adaptor. ThecDNA (33 μl) is brought into contact with 75 ng of vector pT7/T3-18 (5μl), 120 ng of adaptor (1 μl ) of the following sequence (comprising anApa1 site), 5′AAAAAAAAAAAAAGGGCCCG 3′10 μl of a 200 mM NaCl solution, and the mixture is incubated for 5minutes at 65° C. and then the reaction mixture is allowed to cool toroom temperature. The next stage consists in ligating the cloning vectorand the single-stranded cDNA in a reaction volume of 100 μl with 32.5units of the enzyme T4 phage DNA ligase (Pharmacia) overnight at 15° C.in a buffer having the composition: 50 mM Tris-HCl pH 7.5; 10 mM MgCl₂,1 mM ATP. The proteins are then removed by extraction with phenolfollowed by extraction with chloroform and then a 1/10 volume of a 10 mMammonium acetate solution and 2.5 volumes of ethanol are added. Themixture is centrifuged, the pellet is taken up in the buffer having thecomposition: 33 mM Tris-acetate pH 7.9, 62.5 mM potassium acetate, 1 mMmagnesium acetate and 1 mM DTT; the second cDNA strand is synthesized ina volume of 30 μl with 30 units of the enzyme T4 phage DNA polymerase(Pharmacia) and a mixture of 1 mM of the four deoxynucleotidetriphosphates as well as two units of the protein of the T4 phage gene32 (Pharmacia) for one hour at 37° C. The mixture is extracted withphenol and traces are removed by depositing on a P10 column (BiogelP10-200-400 mesh—reference 15011050—Biorad).

The last stage consists in transforming E. Coli MC 1061 cells byelectroporation of the recombinant DNA using a Biorad Gene Pulserapparatus used at 2.5 kV under the conditions recommended by themanufacturer, and then the bacteria are cultured for one hour in LBmedium having the composition:

-   bactotryptone 10 g/l; yeast extract 5 g/l; NaCl 10 g/l.

The number of independent clones obtained is determined by plating a1/1000 dilution from the transformation after a one hour incubation on adish of LB medium supplemented with 1.5% agar (w/v) and with 100 μg/mlof ampicillin called, in what follows, LB agar medium.

The number of independent clones obtained is 1 million.

b) Screening of the cDNA Library.

The entire library was plated on agar medium (Petri dishes 150 mm indiameter) coated with Biodyne A membranes (PALL reference BNNG 132).After leaving overnight at 37° C., the clones are transferred by contactonto new membranes. The latter are treated by placing them on Wathman 3MM paper impregnated with the following solutions: 0.5 N NaOH, 1.5 MNaCl for 5 minutes and then 0.5 M Tris-HCl pH 8, 1.5 M NaCl for 5minutes. After treatment with proteinase K in the following buffer, 10mM Tris-HCl pH8, 10 mM EDTA, 50 mM NaCl, 0.1% SDS, 100 μg/ml proteinaseK for 30 minutes at 37° C., the membranes are thoroughly washed in 2×SSCbuffer (sodium citrate-NaCl), and then dried in an oven under vacuum at80° C. for 20 minutes.

c) Prehybridization and Hybridization of the Membranes.

The membranes are then prehybridized for 2 hours at 42° C. in thefollowing buffer: 1 M NaCl; 30% formamide; 1% SDS; 5× Denhart's 100μg/ml of salmon sperm DNA. After 2 hours of prehybridization, themembranes are hybridized in the same buffer with a concentration ofmouse IL-13Rα probe prepared by nick translation of 2.5×10⁶ dpm/ml, for16 hours. The membranes are washed for twice 30 minutes in 2×SSC, 0.1%SDS buffer at room temperature and then 2 hours at 50° C. in the samebuffer. After overnight exposure at −80° C. in the presence of a KodakX-OMAT film, several positive clones are detected.

d) Sequencing of a Human IL-13Rα Clone and Analysis of the Sequence.

The sequence is obtained using the Applied Biosystem kit (reference401628). The complete nucleic sequence of the IL-13Rα cDNA and the aminoacid sequence deduced therefrom are shown in FIG. 7. The cDNA is 3999bases long excluding the poly-A tail and has a long untranslated 3′region of 2145 bases.

A canonical polyadenylation signal exists at the expected place. Theopen reading frame between nucleotides 34 and 1851 defines a polypeptideof 427 amino acids. The sequence encodes a membrane protein with apotential signal peptide and a single transmembrane domain and a shortintracytoplasmic region.

10 potential glycosylation sites are located in the extracelluar region.It is important to note that two consensus motifs considered assignatures of the type II family of cytokine receptors are also present,the first being derived from an N-terminal disulphide bridge loopstructure, the second being the WSXWS type motif located at theC-terminal end of the extracelluar region.

Example 8 Binding Analyses Carried Out on COS-3 or CHO Cells Transfectedwith Human IL-13Rα cDNA

The CHO cells transfected with the isolated cDNA encoding IL-13Rαspecifically bind labelled IL-13. The Scatchard analysis of thesaturation curve shows a single component site with a Kd value of4.5±0.4 nM and a maximum binding capacity of 26000 receptors/cell (FIGS.8C and 8G).

The results of coexpression experiments are shown in FIGS. 8D and 8H.

Analysis of the results of FIG. 8C shows that IL-13Rα is well expressedin the clone 2036 of the CHO cells. It can be noted that IL-4R displaces60% of the binding of IL-13 in the CHO cells cotransfected with IL-4Rand IL-13Rα cDNA (FIG. 8H) but taking into account a Kd of 7.5 nM forIL-13Rα, there would be 10 times as many IL-13Rα sites as IL-4R sites.

The CHO-hIL4R cells (human IL-4R) expressing hIL-4R which aretransfected with the cDNA encoding hIL-13Rα specifically bind labelledIL-13.

The Scatchard analysis of the saturation curve shows clearly 2 componentsites, one of high affinity with a Kd value of 23±8.9 pM and a maximumbinding capacity of 28000 sites/cell and the other of low affinity witha Kd value of 4.2±1.4 nM and a maximum binding capacity of 150000sites/cell (FIG. 8D).

The second site characterized has the same affinity as hIL-13Rα (humanIL-13Rα) expressed alone and corresponds to the nonassociated IL-13Rαchains because they are expressed in a larger quantity than hIL-4R.

These high-affinity receptors reconstituted in the presence of the 2hIL-13Rα and hIL-4R chains are capable of recognizing the 2 cytokines(FIGS. 8D and 8H). This is even clearer on the COS/pSE1 cellscoexpressing the 2 hIL-13Rα and hIL-4R chains in a comparable quantitywhere IL-4 displaces all the binding IL-13.

The affinity of the recombinant human IL-13Rα is comparable to thatdescribed for the mouse IL-13Rα receptor (2-10 nM) (ref. 22).

In contrast to the hIL-13Rβ chain previously described, human IL-13Rαdoes not constitute, on its own, a high-affinity binding site.

IL-13Rα and IL-4R therefore interact in the cell membrane toreconstitute a high-affinity receptor.

Example 9 Activation of the STAT Proteins by IL-13 and IL-4 in the CHOCells Coexpressing hIL-13Rα and hIL-4R

In human PBMC cells, hIL-4 and IL-13 activate 2 tyrosine kinases of thejanus family, Jak1 and Jak2 which phosphorylate a latent transcriptionfactor, STAT6. This activated factor enters the nucleus and binds tospecific elements in the promoters of the genes regulated by IL-4.

We chose the Cε element of the human Cε promoter as probe in anelectrophoretic mobility switch assay (EMSA) to demonstrate theactivation by IL-13 of a binding factor similar to STAT6.

The nuclear extracts of the CHO cells, expressing IL-13R alone, IL-4Ralone, or the 2 chains together, stimulated with 100 ng/ml of IL-13 orIL-4 for 30 min at 37° C., are incubated with the radiolabelled Cεelement.

The nuclear extracts of the cells coexpressing hIL-13Rα and hIL-4R forma complex having the same mobility in EMSA whether the cells are inducedwith IL-4 or IL-13 (cf. FIG. 9). On the other hand, with the cellsexpressing either chain alone, no complex is detected.

In the CHO cells expressing hIL-13Rα and hIL-4Rα, IL-13 and IL-4therefore initiate the same signalling cascade.

The cloning of IL-13Rβ and IL-13Rα described here makes it possible toimprove the knowledge of the factors involved in the responsesspecifically induced by IL-13 compared with the responses induced byIL-4. It makes it possible, in addition, to have a tool for studying theregulation of the expression of the receptor under normal andpathological conditions where IL-13 plays a key role.

Moreover, the availability of cDNA makes it possible to facilitate thecloning of other proteins necessary for the reconstitution of anIl-4/IL-13 receptor complex and is also useful for the manufacture orthe rational modelling of new medicinal products capable of beingspecific antagonists of the activities of IL-13.

REFERENCES

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1-43. (canceled)
 44. A purified polypeptide comprising an amino acidsequence selected from the group consisting of: (a) the sequence SEQ IDNO:4, and (b) any sequence derived from SEQ ID NO:4 and capable ofbinding specifically to IL-13 and/or of participating in thetransduction of the signal specifically produced by IL-13 at the cellmembrane, and/or capable of interacting with the receptor specific forIL-4 (IL-4R/gp140) to form a complex capable of binding IL-4 and IL-13.45. The polypeptide of claim 44 characterized in that it is a solubleform extending up to residue 343 and preferably up to residues between336 and
 342. 46. A pharmaceutical composition comprising, as activeingredient, a polypeptide according to claims 44 or
 45. 47. A method forscreening for compounds capable of modulating IL-13 receptor alphaactivity comprising the steps of: (a) mixing said compound with a cellexpressing IL-13 receptor alpha on its surface under conditions thatallow binding of said compound to said receptor and; (b) measuring thechange of IL-13 receptor activity to the activity in a control cellexpressing IL-13 receptor alpha that has not been mixed with saidcompound.
 48. The method of claim 47 wherein said compound is anagonist.
 49. The method of claim 47 wherein said compound is anantagonist.